1. Field of the Invention
The present invention relates to an optical disc having formed thereon lands and grooves, which form together a data recording track, and an optical disc drive for the optical disc.
2. Description of Related Art
Well-known data recording media include optical discs such as a magneto-optical type, phase-change type and the like. They include a read-only ROM disc, a recordable disc, a recordable/reproducible RAM disc, a so-called partial ROM disc having a ROM area and a RAM area, etc.
In addition, some of the optical discs called land/groove recording type optical discs, have been proposed which are designed to record data at both lands and grooves for a larger capacity of data storage.
In these conventional optical discs, a recording track is wobbled to provide a servo control information and address information (ADIP) for data recording and reproduction. In the conventional optical discs, however, a recorded data, when reproduced, will be deteriorated due to an amount of light varied, and a light polarizing direction disturbed, by the wobbling, and thus will show a poor signal-to-noise ratio. The influence of this wobbling on a data recording into an optical disc with a high density using a large NA, for example, is not negligible.
For a higher density of data recording into an optical disc, a clock mark is necessary which is highly reliable and can reproduce a data-independent clock. FIG. 1 shows a conventional clock mark by way of example. It is inserted in a wobble signal. The clock mark is formed as a pattern having a greater length than the diameter of a focused laser spot and wobbled towards the outer and inner circumferences, alternately, radially of an optical disc, so that a varied amount of light will result in an S-shaped signal waveform. Thus, a clock reproduced from such a clock mark is not influenced by MTF of a reproducing optical system and has a good signal-to-noise ratio.
For detecting a clock from such a clock mark, a radial push-pull signal is used. Thus, the clock generated from the clock mark will be affected by a tracking offset and radial tilt of an optical disc. Therefore, no stable clock can be reproduced from the clock mark if a tracking error or the like takes place.
Also, it is desired to improve the accuracy of clocking by increasing the number of clocks. However, a clock mark having a correspondingly increased length will greatly cause data to be recorded with a greater redundancy, thus no higher density of data recording can be attained.
Further, for a higher density of data recording into an optical disc, it is desired to reduce the thickness of the substrate of an optical disc while increasing the NA for irradiation to the optical disc. However, such a reduced thickness of the optical disc substrate will greatly affect the disc substrate itself. Namely, the disc substrate will be deflected or distorted due to a variation of environmental conditions. In addition, the manufacturing cost for such an optical disc with a reduced substrate thickness will be greater because it will include costs for prevention of such environmental influences. To avoid such deformation of the optical disc, an optical disc drive may incorporate a disc tilt detecting mechanism to correct a relative angle between a laser beam and main side of an optical disc. However, the disc tilt detecting mechanism will add to the manufacturing costs for such an optical disc drive.
Accordingly, it is an object of the present invention to overcome the above-mentioned drawbacks of the prior art by providing an optical disc suitable for data recording with a high density, and an optical disc drive for the optical disc.
The above object can be accomplished by providing, according to the present invention, an optical disc having address areas discretely disposed on only one of two walls forming together a groove and in each of which an address information is recorded by wobbling, and a data area defined between two walls, not wobbled, of the groove.
According to another aspect of the present invention, an optical disc is provided in which an address information is recorded, by wobbling, on only one of two walls forming together a groove to physically isolate recorded data from an area where the address information is recorded.
According to another aspect of the present invention, an optical disc is provided which has tilt pattern areas discretely disposed and different in radial spatial frequency from other areas on a recording track.
According to another aspect of the present invention, an optical disc is provided in which an address information is recorded on only one of two walls forming together a groove, recorded data is physically isolated from the area where the address information is recorded, and a reflected light of a laser beam irradiated to a tilt pattern area becomes radially asymmetrical when a relative angle of the laser beam irradiated to a recording track varies radially.
According to another aspect of the present invention, an optical disc is provided which has clock areas discretely disposed on a recording track and different in light reflection from tangential forward and rearward portions of a recording track.
According to another aspect of the present invention, an optical disc is provided in which a reflected light of a laser beam irradiated to a clock area is different in amount of light before the clock area from after the clock area. A tangential push-pull signal is detected, based on the difference in amount of light to reproduce a clock.
According to another aspect of the present invention, an optical disc is provided which has clock areas discretely disposed on a recording track and different in light reflection from tangential forward and rearward portions of a recording track.
According to another aspect of the present invention, an optical disc is provided in which a tangential push-pull signal is detected based on a difference in amount of reflected laser beam to reproduce a clock and a reflected light of a laser beam irradiated to a tilt pattern area becomes radially asymmetrical when a relative angle of the laser beam irradiated to a recording track varies radially.
According to another aspect of the present invention, an optical disc is provided which has address areas discretely disposed and in which an address information is recorded by wobbling on only one of the two walls forming together a groove, data area defined between two walls, not wobbled, of the groove, and clock areas discretely disposed and different in light reflection from tangential forward and rearward portions of a recording track.
According to another aspect of the present invention, an optical disc is provided in which an address information is recorded on only one of two walls forming together a groove, recorded data is physically isolated from the area where the address information is recorded, and a tangential push-pull signal is detected, based on the difference in amount of reflected light of a laser beam irradiated to a clock area to reproduce a clock.
According to another aspect of the present invention, an optical disc is provided which has tilt pattern areas discretely disposed and different in radial spatial frequency from other areas on a recording track.
According to another aspect of the present invention, an optical disc is provided in which an address information is recorded on only one of two walls forming together a groove, recorded data is physically isolated from the area where the address information is recorded, a tangential push-pull signal is detected based on the varied amount of reflected light of a laser light irradiated to a clock area to reproduce a clock, and a reflected light of a laser beam irradiated to a tilt pattern area becomes radially asymmetrical when a relative angle of the laser beam irradiated to a recording track varies radially.
The above object can also be accomplished by providing an optical disc drive which is to play an optical disc having formed concentrically or spirally thereon lands and grooves forming together a data recording track and in which an address information is recorded on only one of the two walls forming a groove by wobbling and which has address areas discretely disposed and data area disposed between two walls, not wobbled, of the groove, and comprises a recording/reproducing means for reproducing an address information from the optical disc, and recording or reproducing data based on the address information.
According to another aspect of the present invention, an optical disc drive is provided in which a recording/reproducing means records and reproduces data into and from a data area physically isolated from an area in which the address information is recorded.
According to another aspect of the present invention, an optical disc drive is provided which is to play an optical disc which has formed concentrically or spirally thereon lands and grooves forming together a recording track, and address areas discretely disposed on only one of the two walls forming together a groove and in which an address information is recorded by wobbling, data area disposed between two walls, not wobbled, of the groove, and clock areas discretely disposed and different in light reflection from tangential forward and rearward portions of the recording track, and comprises a recording/reproducing means for detecting a tangential push-pull signal indicative of a tangential difference in amount of light of a laser beam irradiated to the clock area, reproducing an address information, and recording or reproducing data based on the address information, and a clock generating means for generating a clock for the above data.
According to another aspect of the present invention, an optical disc drive is provided in which a recording/reproducing means detects a tangential push-pull signal based on a varied amount of light of a laser beam irradiated to a clock area, and a clock generating means reproduces a clock.
According to another aspect of the present invention, an optical disc drive is provided which is to play an optical disc which has formed concentrically or spirally thereon lands and grooves forming together a data recording track, and address areas discretely disposed on only one of the two walls forming together a groove and in which an address information is recorded by wobbling, data area disposed between two walls, not wobbled, of the groove, and clock areas discretely disposed and different in light reflection from tangential forward and rearward portions of the recording track, and comprises a recording/reproducing means for detecting a tangential push-pull signal indicative of a tangential difference in amount of light of a laser beam irradiated to the clock area, reproducing an address information, and recording or reproducing data based on the address information, and a clock generating means for generating a clock for the above data.
According to another aspect of the present invention, an optical disc drive is provided in which a recording/reproducing means records and reproduces data into and from a data recording area physically isolated from an area in which an address information is recorded. Also an optical disc drive is provided in which a recording/reproducing means detects a tangential push-pull signal based on a difference in amount of light of a laser beam irradiated to a clock area and a clock generating means reproduces a clock. Further, an optical disc drive is provided in which a recording/reproducing means detects a radial push-pull signal indicative of a radial difference in amount of light of a laser beam.